// Set I2C alternative pins
PORTMUX_CTRLB |= PORTMUX_TWI0_bm;
TWI0.SADDR = 0x20 << TWI_ADDRMASK_gp /* Slave Address: 0x20 */
| 0 << TWI_ADDREN_bp; /* General Call Recognition Enable: disabled */
// TWI0.SADDRMASK = 0 << TWI_ADDREN_bp /* Address Mask Enable: disabled */
// | 0x0 << TWI_ADDRMASK_gp; /* Address Mask: 0x0 */
TWI0.SCTRLA = 1 << TWI_APIEN_bp /* Address/Stop Interrupt Enable: enabled */
| 1 << TWI_DIEN_bp /* Data Interrupt Enable: enabled */
| 1 << TWI_ENABLE_bp /* Enable TWI Slave: enabled */
| 1 << TWI_PIEN_bp /* Stop Interrupt Enable: enabled */
| 0 << TWI_PMEN_bp /* Promiscuous Mode Enable: disabled */
| 0 << TWI_SMEN_bp; /* Smart Mode Enable: disabled */
TWI0.SCTRLA |= TWI_ENABLE_bm; // Enable